Acoustic device



R. C. BENDERv ACOUSTIC DEVICE May 5, 1931.

' Filed March 4, 1950 3 Sheets-Sheet l 6 firMo/vp 05a /4 R; c. BENDER cousnc DEVICE May 5,1931;

Ril'ed March 4,' 1930 3 Sheets-Sheet 2 gnu J on f/l/MOMD 656/4 BEA/DEB W 1931. R. c. BENDER 1,804,306

ACOUSTIC DEVICE Filed March 4, 1930 3 Sheets-Sheet 3 A IEWVMOND CEc/L BEA/D516 Patented May 5, 1931 RAYMOND CECIL BENDER, OF WEST PALM BEACH, FLORIDA ACOUSTIC DEVICE Application filed. March 4, 1930. Serial N'o. 433,077.

1 My invention relates to acoustic devices, and more especially to acoustic amplifiers for coupling a sound translating device, such as a sound emitting or sound responsive element, with the surrounding atmosphere, with particular reference to an amplifier or sound chamber for use with a sound emitting element of the type embodying an electromagnetically driven cone, to be used for the reproduction of radio broadcast signals, or elec trical sound reproduction in general.

Among the objects of the invention are the following:

To generally improve the quality of sound reproduction in a device of the above type especially through the elimination of the harshness of tone and the added drumming sounds prevalent in the usual bafile board cone speaker or large exponential horn;

To provide a loud speaker having a horn or amplifying chamber of a shape operative to enhance thequality of reproduction and at the same time adaptable to embodiment in various decorative forms such as birds, mam mals and other objects, without Wide departure from its functional form;

To provide a novel arrangement of cone speaker and bafile board mounting whereby the sound waves emitted from the rear of the speaker may be utilized to reinforce those emitted from the front;

To provide a loud speaker adapted to outdoor use as in a garden or court without protection against weather, insects, small birds and the like.

Other objects and advantages of the invention will be apparent from the following specification and drawings accompanying the same.

In the drawings:

Figure 1 is a longitudinal cross sectional elevation taken on the line 1-1 of Fig. 2;

Fig. 2 is a front elevation;

Fig. 6 is an enlarged fragmentary cross section on the line 33 of Fig. 1;

Fig. 4 is a section on the line H of Fig. 1;

Fig. 5 is a fragmentary front elevation of a radio receiving set with baflie board speaker embodying the main feature of the invention and Fig. 6 is a section on the line 6-6 of Fig. 5.

Referring to the drawings in particular, the resonator or sound amplifying chamber 1 is generally egg-shaped in form and everywhere oval in section with continuously varying area of cross section throughout. This feature enables the device as a whole to be embodied in various different shapes such as that of birds, mammals, houses or other objects without departing from its required general form, the present embodiment of the device being in the form of a great auk. Because the dimensions preferably bear a given ratio to the wave length of the lowest tone to be transmitted the device is relatively large compared to the usual loud speaker, a device in the form here shown and actually built and operated being approximately eight feet in height.

The egg-shaped amplifying chamber is positioned with the smaller portion at the top and the larger portion at the bottom. A pair of relatively small sound openings 2 and 3 is provided at the ends of the chamber, one at the top or smaller end situated in the bottom of the beak 4 of the bird-shaped chamber, and the other at the bottom of the chamber in the bottom of the tail portion. The bottom small opening communicates with the main chamber lthrough a cone shaped extension 5 of the main chamber, forming the tail of the bird, while the top small opening 2 communicates with the main chamber through extended portions 6, 7 and 4 of the main chamgerdforming the neck, head and beak of the Intermediate the ends the chamber 1 is provided with a relatively large sound opening 8. Near the upper or smaller end of the amplifier chamber 1, intermediate the large opening 8 and the top small opening, is mounted a battle board 9 by means of threaded rods or bolts 10 anchored in the walls of the chamber as indicated at 11 and secured to the baffle board by nuts 12. As shown in Fig. 4 the baflie board 9 is provided with the usual central sound opening 13, and in addition to this is formed to provide a series of sound openings or passages 14 surrounding the main opening. It will be obvious that instead of providing these passages in the form of reentrant portions in the periphery of the board, they may take the form of openings of similar area within the periphery around the main central opening. A cone speaker or sound emitting device 15 preferably of the convex side of the cone are directed into the smaller, upper portion of the amplifying chamber. This upper portion of the chamber, including its extension into the neck and head portions, being of general tapering form terminating at a relatively small opening 2, forms in effect a partial air impedance operating to pass a large portion of the higher v. tones which emerge through the opening at the beak, while reflecting or cushioning back a portion of the sound waves which pass down through the side openings in the baffle board into the lower or large portion of the chamber reinforcing those emitted from the front of the cone. 1 have found that the tone quality is greatly improved by making the length of this rear air impedance reflector, that is, the distance from the battle board to the opening 2, at least one half the wave length of the lowest note which it is desired to reproduce. Also a large portion of the sound directed against the sides of the chamber from the back of the cone is reflected down through the side openings in the board to further reinforce the sound waves from the front of the cone.

At the bottom of the amplifying chamber, the inverted cone shaped extension 5 acts as an air impedance to reflector cushion back a large portion of the lower components, permitting a large portion of the higher components to pass outthrough the lower small opening 3. Substantially, all the lower components issue out of the main opening 8 and as this opening is in the side of the chamber in a plane parallel to the direction of propagation of the incident waves from the cone, only a relatively small amount of the waves pass directly from the dynamic speaker into the open air, the greater portion being permitted to build up within the chamber to the desirable point of sound .elhciency. To this end it is preferable to make the distance from the cone speaker element to the lower small opening'3, not less than one half the wave length of the lowest note desired to be reproduced.

' To enablethis building up to take place without undue reverberation, I place within the chamber several absorption pads 16, at. the places indicated, to efiect the. desiredamount of damping. This application of the absorption pads together with the peculiar shape of the resonating or amplifying chamber, results in the elimination of the harsh resonance, drumming sound, and barrel tones prevalent in the usual dynamic speaker with bafile board, exponential horns and the like.

By arranging the upper opening 2 under the beak 1 and providing the short vertical water baiile wall 17 at the back of the beak, the upper opening to the atmosphere is shielded. against the weather. To camouflage the several openings, especially the large opening 8, these are all covered with suitable screenmat-erial 18, which also enhances the tone effect and protects the interior of the device against insects and small birds and animals. For decorative effect electric light bulbs 19 are used for the eyes of the-bird'figure, and another light 20 is mounted within the amplifying chamber near the speaker, the lights 19 giving light to the beak opening and eyes, and the light 20 giving light to the body interior.

To enable the device to be positioned with the main opening S'fa-cing in any desired direction, it is mounted on the base 21 by means of a swivel connection 22 through which passes a conduit 23 for the admission of a suitable multiple conductor cable 24 for conveying current to the speaker element and electric light bulbs.

The casing or walls of the amplifying chamber and the base 21 may be constructed of any suitable material, preferably of some hard material, the present embodiment being constructed of reinforced concrete or cement. The amplifying chamber 1 of general eg shaped form modified, in the present instance, to represent the body of a bird, is made by forming a cage work of iron reinforcing rods 25 in the general contour of a bird, covering this frame or cage work with expanded metal lath 26 fastened to the rods 25 of the cage work, and then applying tothe metal lath a thickness of one half to three inches of cement, stucco or concrete 27 etween and on both inside and outside the lathing and rods to form a smooth solid wall. The swivel elements are molded into the body 1 and base 21, as indicated in Fig. 3 where it will be seen that the swivel spindle element 22 is threaded at the top into a flange 28 in which the lower ends of the reinforcing rods 29 are secured by bolts 30, the flange 28 being invested in the cement 27 along with the rods29, A socketv memberBl for the swivel spindle 22is embedded in the concrete base member 21. The top of this socket member is'provided with a flange 32 which functions as a thrust bearing for the bottom surface of the flange 28, while the sides. of

the socket vmember are provided with fins 33 to anchor 'itin thecement-base. The cable conduit 23 extending down through the tubular swivel spindle 22, is held in place by the cement filling 26, the filling also holding in place an extension 34 of one of the reinforcing rods bent laterally at the lower end so as to engage a fixed stop 35 to limit the turning movement of the swivele'd amplifier chamber. As shown atthe bottom of Fig. 1, and indicated in dotted lines in Fig. 2, a tunnel 36 is formed in the bottom of the base 21 to house the cable 24 leading away from the device to the usual necessary sources of signal and power current not shown.

Referring to Figs. 5 and 6, these show one of the main features of the invention applied to the usual combination of a cone speaker and baflle board mounted in a radio receiving cabinet 37. Here the outer openings 38 in the bathe board 39 take the form of a series of openings through the board within the periphery of the board and outside the edge of the cone 40 and the main or central opening 41. Mounted within the speaker compartment of the cabinet, and surrounding the back or rear side of the cone 40, is a tone or resonating chamber 42 which, like the small tapered portion 6 of Fig. 1, is tapered away from the cone 40 to form a conical air impedance reflector with a relatively small opening 43 at the back. It has been found that the presence of the apertures or openings 38 in the baffle board greatly reduces the harshness without detracting from the usual amplifying qualities of the ba-flie board and that the use of the reflector 42 greatly improves the amplifying effect and its quality while the opening 43 in the back of the tone chamber or reflector 42 (corresponding to the opening 2 in the beak in Fig. 1) prevents the drumming sound and sound wave distortion. In this embodiment, as in that of Figs. 1 to 4, the effect of the tone chamber and reflector 42 with its relatively small opening 43 is to reflect or cushion back a large portion of the sound waves emitted from the back of the cone, causing them to be projected through the openings 38 to the front of the board 39 where they reinforce the sound waves eminating from the front of the cone 40 through the main central opening 41. Those sound waves which pass out through the opening 43 are projected into the surrounding atmosphere outside the cabinet by way of the rear cabinet opening 44.

While certain specific embodiments of the invention have been described herein for the sake of disclosure, it will be obvious to those skilled in the art that many modifications and variations thereof may be made without departing from the spirit of the invention and I therefore do not limit myself to what is shown in the drawings, but contemplate all such modifications and variants as fall fairly within the scope of the appended claims.

Having thus described my invention what I claim and desire to secure by Letters Patent is: i

1. A loud speaker comprising a sound amplifying chamber of general tapered form and the convex side facing inthe general direction of the smaller end.

I 2. A loud speaker as claimed in claim 1 in which a battle board having a plurality of openings is mounted partitioning the large and small ends of the chamber and in which the concave side of the diaphragm communicates with the large end of the chamber through one of said openings, another of said openings being arranged to permit communication between said larger and smaller ends of the amplifying chamber.

3. A loud speaker comprising a tapered egg-shaped sound amplifying chamber having sound openings near the large and small ends respectively, a baffle board mounted within the chamber intermediate the ends thereof, an opening in the balfle board, a conical sound emitting diaphragm situated between the baflle board and the small end of the chamber with the concave surfaceof the diaphragm in communication with the large end of the chamber through the opening in the baffle board, said bafiie board being provided with another opening for communication between the large and small ends of the chamber outside the diaphragm.

4. A loud speaker comprising a tapered sound amplifying chamber having a relatively small opening at the large end and another relatively small opening at the small end, and a relatively large opening in the side intermediate the ends, a baffleboard partition arranged in the chamber between the small opening at the small and the large opening, said partition having a sound opening therethrough, a sound emitting diaphragm arranged to emit sound waves from one side into the small end of said, chamber and from the opposite side into the large end of said chamber through the said opening in said baflle board, said baffle board having another sound opening therethrough arranged to permit the passage of sound waves from the small end of the chamber into the large end.

5. An acoustic device comprising an elongated sound amplifying chamber of irregular cross section having relatively small openings at opposite ends, a baffle board diaphragm situated intermediate the ends of the chamber dividing it into two compartments, one of relatively small area and the other of relatively large area, said chamber being tapered abruptly from thebafile board toward one end for a distance less than one half the total distance and to an area less than that of the baffle board and continuing on to the opening with an area less than that of the baifie board, and enlarged from the balile board to substantially the remainder of its extent toward the other end to an area greater than that of the baflie board, said baffle board having an opening, and a conical sound emitting diaphragm mounted with its concavesurf'ace toward the opening in the baffle board to emit sound therethrough, said baiile board being provided with another opening or passage to permit sound waves emitted from the convex side of the sound emitting diaphragm to pass from the smaller compartment of the amplifying chamber into the larger compartment.

- 6. A loud speaker comprising a tapered, egg-shaped sound amplifying chamber having an extension at its larger end in the form of an inverted cone with a relatively small opening near the apex of the cone, said chain ber'having a relatively large opening intermediate the ends,and a sound emitting element situated intermediate the small end of the chamber and the large opening.

7. A loud speaker as claimed in claim 6 with a battle board surrounding the sound 7 emitting element and in which the distance 7 between the baffle board and the opening in the cone-shaped extension is not less than one half the wave length of the lowest note to be reproduced.

8. Aloudspeakercomprising anegg-shaped amplifying chamber having a relatively large opening in the side and relatively small'openings, one at each end, respectively, a sound emitting element situated within the chamber intermediate the large opening and the smaller end of the egg-shaped chamber, and absorption pads mounted against portions of the in.- nerwalls of said chamber to prevent resonance and reverberation.

9. Aloud speaker comprising an amplifying horn of general tapering form from end to end, and a conical sound emitting element situated within and intermediatethe ends of the amplifying horn, the axis of the element being substantially parallel to nal axis of the horn. V v

10. A loud speaker comprising an eggshaped sound amplifying chamber mounted with the smaller endabove and the larger end below, abaffle board mounted within the chamber extending thereacross near the upper smaller end, said baffle board having a central opening and having another opening constituting a sound passage between the upper andlower ends of the chamber, a cone speaker element mounted on the upper side ofthe baffie board within the upper smaller portion of the chamber and adapted to direct soiled Wa d wnwa dly t u 1 central opening in the balile board into the larger portion of the chamber, and to direct sound waves fromv the rear side of the cone toward the upper smaller end of the chamber, a sound conduit extending generally upwardly from the smaller end of the chamber and opening laterally, a lip or eave extending over the. lateral opening of the said conduit, a water protecting wall extending upwardly from the lower edge of the lateral opening of g I the small end with a relatively small opening, 1

baffle board mounted in the chamber and forming one end wall of the largeend of the tone chamber, said baffle board being provided with a plurality of openings, and a conical sound emitting diaphragm mounted on the baffle board over one of said openings, the concave surface of said diaphragm facing the large end of the chamber and the convex surface of the diaphragm facing the small. end of the chamber. n

12. An acoustical device comprising a sound emitting element and a baflie board therefor, said baffle board being provided with openings for the transmission of sound waves from the rear of the elementpast the bafiie board to the space in front thereof, in combination with a reflector casing surrounding the back and the front of the element and the baffie board and provided with sound emitting openings in th'e'rear and in the front of the baffle board.

In testimony whereof I affix my signature.

RAYMOND CECIL BENDER.

the longitudi- 

